IGEBA   23946
INSTITUTO DE GEOCIENCIAS BASICAS, APLICADAS Y AMBIENTALES DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Provenance analysis of the Toro Negro Formation, La Rioja Province, Argentina.
Autor/es:
AMIDON, W.H.; FISHER, G.B.; MARENSSI, S.A.; BURKANK, D.W.; CICCIOLI, P.L.; LIMARINO, C.O.; KYLANDER-CLARK, A.
Lugar:
Santa Rosa
Reunión:
Congreso; VII Congreso Latinoamericano de Sedimentología y XV Reunión Argentina de Sedimentología; 2016
Resumen:
Detrital zircons and modes of sandstones and conglomerates were used to analyze the provenance of the Toro Negro Formation (late Miocene-early Pliocene) at La Troya creek, Vinchina Basin, La Rioja province. This basin, located in the Western Sierras Pampeanas, is bounded to the north and south by Toro Negro and Umango-Espinal ranges, to the west by the Precordillera and Cordillera Frontal and to the east by the Famatina System. The Toro Negro Formation (~2500 m thick, Turner 1964) together with the underlying Vinchina Formation represents one of the thickest and longest continually exposed foreland sections in northwest Argentina. The Toro Negro Formation was divided into lower and upper members by Ramos (1970) and further into three depositional sequences (DS I, II, and III, Ciccioli et al., 2014). The lower member is split between DSI and II and the upper member is equivalent to DSIII.Three sandstone petrofacies (plutonic-metamorphic, volcanic and mixed petrofacies) and three conglomerate lithic associations (basement, sedimentary and volcanic lithic) were recognized, which allowed the establishment of three source areas: Western Sierras Pampeanas (Toro Negro and Umango Ranges), Cordillera Frontal and Precordillera. Detrital zircon samples provided 7 U-Pb age populations: (1) Mesoproterozoic, (2) Neoproterozoic-Cambrian, 3) Ordovicic-Siluric, 4) Devonian-Carboniferous, 5) Permo-Triassic, 6) Jurassic-Cretaceous and 7) Cenozoic.The integrated analysis shows that in the Lower Member of the Toro Negro Formation, the Sierras Pampeanas (mainly the Toro Negro Range, Mesoproterozoic and early Paleozoic) was the main source, with secondary sediment supply from the Frontal Cordillera (Permo-Triassic and Cenozoic) and the Precordillera (Devonian-Carboniferous and Mesozoic). On the contrary, the upper member exhibits a progressive increase in the supply from the eastern Precordillera (Devonian-Carboniferous ages), next to the west, with secondary source from Sierras Pampeanas and Cordillera Frontal. The coexistence of the three source areas demonstrates that the evolution of this type of basin is much more complex than previously envisaged. Therefore, an integrated analysis using different tools (sedimentary facies, paleocurrent measurements, sandstone and conglomerate composition and geochronological dating of detrital zircons) is needed for a clearer understanding of broken-foreland basins.Ciccioli, P.L., Marenssi, S.A. y Limarino, C.O., 2014. Petrology and provenance of the Toro Negro Formation (Neogene) of the Vinchina broken foreland basin (Central Andes of Argentina). Journal of South American Earth Sciences 49: 15-38.Ramos, V.A., 1970. Estratigrafía y estructura del terciario en la Sierra de los Colorados (provincia de La Rioja), Republica Argentina. Revista de la Asociación Geológica Argentina 25: 359-382.Turner, J.C.M., 1964. Descripción geológica de la Hoja 15c, Vinchina, provincia de La Rioja. Buenos Aires. Dirección Nacional Geológica. Minería Boletín 100: 81.